This invention relates to an improved process, and the catalyst which achieves this process, for making ethylene glycol and methanol directly from synthesis gas, i.e., mixtures of hydrogen and oxides of carbon. More particularly, this invention achieves the production of ethylene glycol and methanol directly from synthesis gas in the presence of a catalyst which is a ruthenium carbonyl complex and an organosilicon compound having a hydrogen bonded to silicon under process conditions which heretofore were regarded as being incapable of producing ethylene glycol and methanol with a ruthenium containing catalyst.
Ruthenium has been explored as a catalyst by many. It has been considered as a hydrogenation catalyst, as a hydroformylation catalyst, as a catalyst to produce a wide range of monohydric alcohols (non-specific as to any of them) exclusive of methanol, as an alcohol homologation catalyst such as for the conversion of methanol to ethanol,* and as a high pressure catalyst to selectively produce methanol and methyl formate. FNT *See, for example, U.S. Pat. Nos. 4,133,966 and 3,285,948; and Japanese Patent Application (Kokai) No. 52-73804/77 (June 21, 1977) [Application No. 50-149391/75 (application date, Dec. 15, 1975)] to Mitsubishi Gas Chemical Industry Company.
In Gresham, U.S. Pat. No. 2,535,060, there is described a process for preparing monohydric alcohols by introducing carbon monoxide, hydrogen and a hydroxylated solvent into a reaction vessel and heating the mixture in the presence of a ruthenium-containing substance and an alkaline reagent which controls the pH within the range of 7 to 11.5, at a temperature within the range of 150.degree. to 300.degree. C. under a pressure within the range of 200 to 1,000 atmospheres.
Solid ruthenium dioxide is used in Examples 1 and 2 of the Gresham patent. At column 2, lines 30-33 of the patent, the patentee states his belief that ruthenium dioxide is reduced in situ during the reaction. Example 1 compares the use of a number of solutes such as phosphoric acid, acidic phosphate buffer, no solutes at all, ammonia and sodium bicarbonate. In this example, the solvent was water. In Example 2 of Gresham, a number of alcohols were characterized as solvents.
Gresham states that ruthenium and its compounds are "specific" in their effect upon this reaction and other catalysts "do not lead to straight chain primary alcohols under the conditions of this process". There is no indication that Gresham's process, as operated by him, produced ethylene glycol.
Gresham's work should be contrasted with his earlier work described in U.S. Pat. No. 2,636,046, filed Oct. 16, 1948. In this patent, Gresham describes the production of polyfunctional oxygen-containing organic products including such compounds as ethylene glycol, glycerine, and the like.* FNT *Note Rathke and Feder, JACS, 100, pp. 3623-3625 (May 24, 1978); Ann. N.Y. Acad. Sci., 333, 45 (1980).
This is accomplished by the reaction of hydrogen with carbon monoxide in the presence of a solvent to produce glycol. According to this patent, the reaction of carbon monoxide with hydrogen must be at pressures of above 1,000 atmospheres and "particularly above a minimum of about 1,400 atmospheres" in order to obtain the "polyfunctional oxygen-containing organic compounds . . . in excellent yield" (column 2, lines 9-17). The patent specifically states at column 2, lines 37-43, that
"[I]n the hydrogenation of oxides of carbon at pressures of 1,000 atmospheres and below, virtually no polyfunctional compounds are produced. At pressures above 1,000 atmospheres and especially at pressures of about 1,500 to 5,000 atmospheres preferably 2,000 to 5,000 atmospheres, polyfunctional compounds are obtained." PA0 "The reaction products usually contain virtually no hydrocarbons, acids, esters, or branched-chain alcohols. These results were entirely unexpected, in view of the existing knowledge of the catalytic reaction between carbon monoxide and hydrogen in the presence of alcohols and Group VIII metal catalysts." PA0 "It should be emphasized here that, under the conditions of temperature, pressure and gas ratios just described, no reaction takes place between carbon monoxide and hydrogen in a liquid medium (water or alcohol) if one of the common group VIII metals, such as cobalt or nickel, is used as the catalyst. This is evidenced by the fact that, using, for example, a cobalt catalyst, no significant drop in pressure is observed when carbon monoxide and hydrogen are contacted under the conditions recited. Ruthenium is thus unexpectedly different from these related metals." (Column 4, lines 19-30.)
Though the examples of the patent describe the use only of cobalt catalyst, the patentee, at column 3, line 61, indicates that the catalyst may contain "cobalt, ruthenium, etc." According to the patentee, the most outstanding results are obtained by using a catalyst containing cobalt, especially compounds of cobalt which are soluble in at least one of the ingredients of the reaction mixture.
Prior to the filing of U.S. Pat. No. 2,535,060 and subsequent to the filing of U.S. Pat. No. 2,636,046, there was filed on Apr. 12, 1949, a commonly assigned application by Howk, et al. which issued as U.S. Pat. No. 2,549,470 on Apr. 17, 1951. The Howk, et al. patent is directed to a catalytic process for making monohydric straight chain alcohols and does not mention the production of ethylene glycol. The patent emphasizes the production of straight chain primary hydroxyalkanes having from 3 to 50 or more carbon atoms in the molecule. This, the patent states, is accomplished by introducing hydrogen, carbon monoxide and a hydroxylated solvent into a reaction vessel, and heating the mixture in the presence of a catalyst of the class consisting of ruthenium metal, ruthenium oxide and ruthenium carbonyl, at a pressure within the range of 200 to 1,000 atmospheres and at a temperature within the range of 100.degree. to 250.degree. C. The liquid hydroxyl-containing reaction medium may be water or alcohol, preferably a primary hydroxyalkane having from 1-10 carbon atoms per molecule. According to the patentee, a substantial proportion of the reaction product usually consists of alcohols containing more than 6 carbon atoms per molecule. The patent goes on to state (column 1, line 50, et seq.):
According to the Howk, et al. patent:
The numbered examples indicate an apparent preference for making normal-monohydric alcohols, with the proportion of pentane soluble to pentane insoluble alcohol being at least 2:1. In one example, starting at the bottom of column 6 of Howk, et al., the solvent employed is characterized as a carboxylic acid or anhydride rather than the neutral hydroxylated solvents which were described in the other examples. This comparative example demonstrated that in a process operated at 200.degree. C. for 18 hours using pressures maintained in the range of 300-950 atmospheres by repressurizing periodically with synthesis gas, there was produced a reaction product containing "a large quantity of wax." According to the author, 40.55 parts of esters boiling from 59.degree. C. at atmospheric pressure to 150.degree. C. at 116 millimeters pressure were obtained and this can be compared to the wax obtained in the amount of 37.06 parts. In that particular example, the patentee appears to have demonstrated that when one does not employ the hydroxylated solvent, the amount of wax essentially equals the amount of pentane soluble alcohol products obtained. This is supported by the statement at column 2 of Gresham U.S. Pat. No. 2,535,060 which refers to Howk, et al. Ethylene glycol diacetate is also observed.
At column 3, lines 54 et seq., Howk, et al. describe the influence that pressure has on the course of the reaction. According to Howk, et al. with pressures up to about 150 atmospheres the reaction products are only hydrocarbons. This appears to be in accord with recent work described by Masters, et al. in German Patent Application (Offenlegungsschrift) No. 2,644,185*, based upon British priority application Specification No. 40,322-75, filed Oct. 2, 1975. Masters, et al. obtained only hydrocarbons at such pressures using a ruthenium catalyst. FNT *See Doyle, et al., J. of Organometallic Chem., 174 C55-C58 (1979), who conclude that the process characterized in the German Offenlegungsschrift involved a heterogeneous Fischer-Tropsch reaction.
Fenton, U.S. Pat. No. 3,579,566, patented May 18, 1971, is concerned with a process of reducing organic acid anhydrides with hydrogen in the presence of a Group VIII noble metal catalyst and a biphyllic ligand of phosphorus, arsenic or antimony. The process of Fenton bears a remarkable similarity to oxo processing conditions to produce aldehydes and alcohols (compare with Oliver, et al., U.S. Pat. No. 3,539,634, patented Nov. 10, 1970) except that Fenton fails to supply an olefinic compound to the reaction. In the Fenton reaction, an acid anhydride, such as acetic acid anhydride, is reduced to ethylidene diacetate in the presence of hydrogen or CO/H.sub.2 and a rhodium halide or a mixture of palladium chloride and ruthenium trichloride catalyst, provided in combination with triphenylphosphine. Ethylene glycol diacetate is also observed. Of particular significance is the fact that none of Fenton's examples produce a methyl ester, as are produced by the process of co-pending U.S. patent application Ser. No. 971,667, discussed below and encompassed herein. Another point is that it is possible that Fenton's ethylidene diacetate can be converted to ethylene glycol diacetate under the conditions of example 1.
W. Keim, et et., (Journal of Catalysis, 61, 359 (1980) has reported that reaction of Ru.sub.3 (CO).sub.12 under very high pressures (2,000 bars) produce mainly methanol and methyl formate, but traces of glycol (0.8 to 1.2 percent of the total products) were also seen. In one experiment a small amount of ethanol was detected. No glycerine was observed in these reactions.
Pruett and Walker, U.S. Pat. No. 3,833,634, patented Sept. 3, 1974, based on an application originally filed Dec. 21, 1971, describe a process for preparing glycols by reacting an oxide of carbon with hydrogen using a rhodium carbonyl complex catalyst. The examples of the patent compare the reaction of hydrogen and carbon monoxide in the presence of the desired rhodium containing catalyst and other metals. In Example 9 of the patent, the reaction was attempted with triruthenium dodecacarbonyl as the catalyst using tetrahydrofuran as the solvent with a reaction temperature of 230.degree. C. for 2 hours, and "the product contained no polyhydric alcohol."
According to Roy L. Pruett, Annals, New York Academy of Sciences, Vol. 295, pages 239-248 (1977), at page 245, metals other than rhodium were tested to determine the production of ethylene glycol from mixtures of carbon monoxide and hydrogen. These metals include cobalt, ruthenium, copper, manganese, iridium and platinum. Of these metals, only cobalt was found to have a slight activity, citing British Pat. No. 665,698 which corresponds generally to the last mentioned Gresham U.S. patent. Pruett stated that such slight activity with cobalt was "qualitatively" in agreement with the results obtained by Ziesecke, 1952, Brennstoff-Chem, 33:385.
In a recent report (Journal of the American Chemical Society, vol. 101, pp.7419-21 (1979)) J. S. Bradley of Exxon Corporation produced methanol and methyl formate at a selectivity greater than 99% without hydrocarbon products detected, by the reaction of systhesis gas (H.sub.2 :CO=3:2) under pressures on the order of 1,300 atmospheres and at temperatures around 270.degree. C. using a Ru catalyst. J. S. Bradley (in "Fundamental Research in Homogeneous Catalysis", ed. M. Tsutsui, vol. 3, Plenum Press, 1979, pages 165 et seq.) discusses the formation of ethylene glycol as reported by Gresham and reports the hydrogenation of carbon monoxide to methanol and methyl formate in the presence of ruthenium carbonyl clusters and under a pressure of about 1300 atmosphere. Bradley concluded at page 175, stating that, "On the basis of these results it seems that claims of homogeneous catalysis of hydrocarbon formation by Ru.sub.3 (CO).sub.12 in solution are probably erroneous."
An interesting exception to the previously report inactivity of ruthenium catalysts to produce glycol is the high pressure (viz. 1650-1750 bars) experiment reported by R. Fonseca, et al., High Pressure Science and Technology, 6th AIRAPT Conference (Chapt. "High Pressure Synthesis of Polyalcohols by Catalytic Hydrogenation of Carbon Monoxide"), pages 733-738 (1979), published by Plenum Press, New York. In this experiment, the authors report the reaction in tetraglyme of a CO:H.sub.2 (1:2 ratio) mixture at 1650-1765 bars, i.e., about 25,000 psi (1,757.6 kg/cm.sup.2) and at 230.degree. C. using triruthenium dodecacarbonyl and 2-pyridinol as a ligand, both in unstated amounts, for a period of 5 hours. The authors report a % conversion of 12.9 (unstated basis), a % yield of polyols of 3 (unstated basis), and % selectivities as follows: ethylene glycol, 22.9 percent; glycerine, 0; and methanol, 16.1 percent. This work was investigated recently and reported by G. Jenner et al., React. Kinet. Catal. Lett., Vol. 15, No. 1 103-112 (1980). The authors therein concluded that ethylene glycol was absent when a Ru.sub.3 (CO).sub.12 catalyst was employed. Further, in Williamson, et al., U.S. Pat. No. 4,170,605, patented Oct. 9, 1979, the patentees report in Examples I and II the reaction in 1-propanol of synthesis gas (CO:H.sub.2 =1:1) at 25,000 psig and at 230.degree. using ruthenium tris (acetylacetonate) and 2-hydroxypyridine, the latter being the same ligand employed by Fonseca et al., supra, for a period of 2 and 3 hours, respectively. In Example I, Williamson, et al. report the production of 4 grams of product* containing (mole percent basis): ethylene glycol, 57% and methanol, 25%. In Example II, 7 grams of product* are reported containing 66 and 16 mole percent of ethylene glycol and methanol, respectively. FNT *Included in the 4 and 7 grams of product are trace amounts of water and methylformate, as well as 16 mole % (Example I) and 15 mole % (Example II) of propylformate. The latter compound would appear to be derived from 1-propanol initially present in the reaction mixture, rather than a synthesis gas-derived product.
Deluzarche, et al., Erdol and Kohle-Erdgas-Petrochemie, Bd. 32, Heft 7, July 1979, pp. 313-316, discloses that pressures over 25,000 psi produce methanol and ethylene glycol from synthesis gas in the presence of a Ru.sub.3 (CO).sub.12 catalyst.
Further, in copending application Ser. No. 091,242, filed Nov. 15, 1979, there is described a process for selectively producing methanol, ethanol, and ethylene glycol by reacting carbon monoxide and hydrogen in a homogeneous liquid phase mixture containing a ruthenium carbonyl complex. The reaction is effected at a temperature between about 50.degree. C. to about 400.degree. C. and a pressure of between about 500 psia (35.15 kg/cm.sup.2) and about 15,000 psia (1,054.6 kg/cm.sup.2) for a period of time sufficient to produce such products; and in copending application Ser. No. 971,750, filed Dec. 21, 1978, there is described an improved process for producing methyl and ethylene glycol esters as described in Ser. No. 091,242 in which the improvement comprises maintaining the combined concentration of methyl ester, ethylene glycol ester and water in the reaction medium at less than about 30 vol.%.
There is disclosed in U.S. patent application Ser. No. 921,698, filed July 3, 1978, in the name of John. F. Knifton, assigned to Texaco Development Corp., a process for the production of alcohol and vicinal glycol esters from synthesis gas by reacting such synthesis gas in a carboxylic acid medium in the presence of a ruthenium catalyst at a temperature of between 100.degree. C. and 350.degree. C. and superatmospheric pressures of 500 psia or greater. In this particular application a co-catalyst species is employed with the ruthenium catalytic species. The co-catalyst is selected from the group consisting of alkali metal salts, alkaline earth salts, quaternary ammonium salts, iminium salts and quaternary aliphatic phosphonium salts.
In U.S. patent application Ser. No. 921,699, filed July 3, 1978 by Knifton, a similar process is described in which the catalyst contains either ruthenium or osmium. However, in this particular application the carboxylates of ethylene glycol are formed without the utilization of a co-catalyst. Essentially the same or similar disclosure as set forth in the aforementioned two patent applications can be found in U.S. Ser. No. 967,943, filed Dec. 11, 1978, and U.S. Pat. No. 4,268,689 which issued. The disclosures of the aforementioned four patent applications can be found in British Patent Publication No. 2,024,811.
U.S. Pat. No. 4,265,828 discloses a process for making ethylene glycol by contacting a mixture of carbon monoxide and hydrogen with a ruthenium-containing compound dispersed in a low melting quaternary phosphonium or ammonium base or salt under a pressure of 500 psi or greater at a temperature of at least 150.degree. C.
The preparation of vicinal glycol ester, e.g., ethylene glycol acetate esters, by the reaction of synthesis gas in the presence of an aliphatic carboxylic acid and a homogeneous ruthenium catalyst is further discussed by J. Knifton, J.C.S., Chem. Comm, page 188 (1981). The ruthenium catalyst precursor is preferably a ruthenium compound in combination with a large cationic species, such as a quaternary phosphonium or quaternary ammonium salts. The presence of the large cationic species was considered to aid in stabilizing an anionic ruthenium cluster during the carbon monoxide hydrogenation sequence.
The hydrogenation of carbon monoxide to methanol and ethylene glycol in the presence of a homogeneous ruthenium catalyst to form ethylene glycol with acetic acid solutions is discussed by B. Duane Dombek, J.Am. Chem. Soc., 102, 6855 (1980). The reaction is reported to produce substantial quantities of methyl acetate, smaller amounts of ethylene glycol diacetate and traces of glycerine triacetate.
In copending application U.S. Ser. No. 278,900, filed concurrently herewith, a process is disclosed for the manufacture of ethylene glycol, methanol, and derivatives thereof from the reaction of hydrogen and carbon monoxide, by a homogeneous catalytic process using as the catalyst a cobalt containing compound and an organosilicon compound having a hydrogen bonded to silicon (--Si--H).
In copending application U.S. Ser. No. 278,878, filed concurrently herewith, a process is disclosed for the manufacture of alcohols and derivatives thereof from the carbon residue of an organosilicon compound wherein such alcohol has one carbon more than the corresponding carbon residue from which it was derived.
As pointed out above, ethylene glycol can be produced directly from a mixture of hydrogen and carbon monoxide using a rhodium carbonyl complex as a catalyst. There has been a substantial amount of work done on the formation of ethylene glycol from mixtures of hydrogen and carbon monoxide in the presence of rhodium carbonyl clusters, such as is disclosed in U.S. Pat. Nos. 3,833,634; 3,878,214; and 3,878,290.
The above discussion provides a characterization of technology heretofore published or filed upon which relates to the direct production of ethylene glycol from mixtures of carbon monoxide and hydrogen or the production of monohydric alcohols from the direct reaction of hydrogen and carbon monoxide in the presence of a ruthenium catalyst.
Owing to the reduced availability of petroleum sources the cost of producing chemicals from petroleum has been steadily increasing. Many have raised the dire prediction of significant oil shortages in the future. Obviously a different low cost source is needed which can be converted into the valuable chenicals now derived from petroleum sources. Synthesis gas is one such source which can be effectively utilized in certain circumstances to make chemicals.
The most desirable aspect of synthesis gas is that it can be produced from non-petroleum sources. Synthesis gas is derived by the combustion of any carbonaceous material including coal, or any organic material, such as hydrocarbons, carohydrates and the like. Synthesis gas has for a long time been considered a desirable starting material for the manufacture of a variety of chemicals and, as discussed hereinabove, homogeneous ruthenium catalysts will produce ethylene glycol and methanol directly from synthesis gas.
However, while previously known processes using homogeneous ruthenium catalysts will produce ethylene glycol and other polyhydric alcohols generally very high pressure are required and it would be desirable to produce ethylene glycol and methanol or derivatives thereof at high process efficiency and low or moderate pressures.